At present, the existing fingerprint identification sensors mainly include optical fingerprint identification sensors, surface acoustic wave (SAW) fingerprint identification sensors and semiconductor identification fingerprint sensors, etc.
The principle of an optical fingerprint identification sensor is the principle of optical photography and reflection, it has the advantages of strong antistatic capacity, low cost and long service life, and its disadvantages are high light dependence, failing to recognize fake fingers, and poor applicability of dry-wet fingers, etc.
A SAW fingerprint identification sensor has disadvantages of large volume and high power consumption, etc.
A semiconductor fingerprint identification sensor mainly uses the principle of capacitance, inductance, temperature or pressure to achieve fingerprint image collection. As the most promising fingerprint sensor, the semiconductor fingerprint identification sensor has been more and more focused by people because of the advantages of high recognition rate (can recognize the fake fingers), small size and low power consumption. But its disadvantages are obvious: using single-crystal silicon as the sensor results in high cost, low signal-to-noise ratio, and poor reliability, etc. The sensing unit of the existing semiconductor fingerprint identification sensor is made of single-crystal silicon substrate; the price is calculated according to the size of single-crystal silicon substrate, so that the cost is rising sharply by increasing the sensor area.